© Martin Vestergaard, some rights reserved (CC-BY-NC) · GBIF
Overview
Podosphaera spp. is a genus of about 60 powdery-mildew fungi in the family Erysiphaceae (kingdom Fungi). It is not a plant but a group of obligate parasites that live on the surfaces of living plants. Members appear as a white to grayish, powdery coating of threads (mycelium) on leaves, shoots, buds, flowers, and fruit, anchored to the host by feeding structures (haustoria) that penetrate the outer cells to draw nutrients. The fungi spread by chains of single-celled spores (conidia) carried on the wind, and many also form tiny, rounded overwintering bodies (chasmothecia), each holding a single spore sac, a feature that helps define the genus. Several species are economically important crop diseases: Podosphaera xanthii causes powdery mildew of cucurbits, Podosphaera leucotricha of apple and pear, Podosphaera pannosa of roses and stone fruit, and Podosphaera aphanis of strawberry. Infection distorts new growth, yellows and curls leaves, and can lower yield and fruit quality. The fungi grow most in warm, humid conditions with poor air movement, and unlike many molds they do not need free water on the surface to infect. They overwinter in buds, plant debris, or as chasmothecia.